We have developed a mathematical model which incorporates two components accounting for both vascular and EV transit of contrast media, described by: C(t) = c * ta * [e(-t/b) + d * [e(-t/h)], where C is contrast concentration, t = time, a, b, and c are vascular gamma-variate fit parameters, and d and h describe extravascular tissue contrast. In 3 pigs, 3 series (at 1.5 min intervals) of 20 sequential scans, acquired every other heart beat, were obtained with electron beam CT. During the first of the series of 3, a bolus of iopamidol (0.33 cc/kg) was administered into the right atrium over 2, 4, or 8 sec. The model fitted well the sampled density values pertaining to contrast handling in both compartments. This model of the myocardial microcirculatory indicator dilution process may be very useful to quantify the function of the in vivo myocardial microcirculation using various imaging methods such as fast CT and magnetic resonance imaging (with a suitable contrast agent such as chelated gadolinium).